Can we transfer two embryos instead of one?
This morning I sat with a young couple to plan their first embryo transfer. Their embryos had been created because of male factor infertility and had been tested with PGT-A, with four of them reported as euploid.
At first glance, transferring two embryos can seem like the obvious choice: twice the embryos, twice the chance. Understandably, they wanted to give themselves the best possible chance.
But two embryos do not give you twice the chance of taking home one healthy baby. They do, however, give you a much higher chance of carrying twins — and twins are not simply "two babies at once", often imagined as a happy bonus. As doctors, we see another side of the story. Compared with singleton pregnancies, twins are much more likely to be born prematurely, require neonatal intensive care, and face long-term complications related to early birth. Mothers also have a higher risk of serious pregnancy complications.
Then I added something that often surprises my patients: even when we transfer only one embryo, nature can still make its own decision. Occasionally, a single embryo divides after transfer and develops into identical twins. Although uncommon, this happens in approximately 1% of ART pregnancies after single embryo transfer.
That means transferring two embryos does not simply increase the chance of twins. It also creates the possibility of triplets, if one of those embryos divides.
My goal isn't simply to help my patients become pregnant. My goal is to help them take home a healthy baby. Whenever we decide how many embryos to transfer, that's the outcome I'm thinking about. It's also the reason I spend so much time discussing this decision with my patients.
All of us — the patient, her partner, and the medical team — share a responsibility to give that future tiny human the best possible chance of entering the world healthy and safe.